Optimizing photoluminescence in carbon dots-Haematococcus pluvialis algae to increase photosynthesis and bioactive compounds.

Light management constitutes an essential strategy that can be applied to increase nutrient output and algal biomass. One emerging approach to dealing with reduced photosynthesis potential is the use of carbon quantum dots (CQDs), which modulate photosynthetic electron transfer. The present study investigates the performance of Haematococcus pluvialis in photosynthesis and biochemical composition, with a focus on different surface functional groups in CQDs and boron-nitrogen-doped carbon quantum dot (BNCQD) nanoparticles. Radical scavenging and MTT tests of the synthesized carbon dots demonstrated that CQDs exhibited strong antioxidant properties (93.7%) and maintained high biocompatibility at all doses tested, while BNCQDs showed dose-dependent mild cytotoxicity. The results showed that treating with CQDs and BNCQDs during cultivation led to increased growth compared to the control group. CQDs had a more dominant effect on increasing growth factors than BNCQDs. Moreover, CQDs accelerated the algae's transition to the red phase. The results showed that enhancing the carboxyl and hydroxyl groups on the surfaces of CQD resulted in a greater increase in metabolic yield compared to BNCQD, which has fewer hydroxyl groups. The current findings highlight the potential of CQDs in microalgae biotechnology, especially in enhancing photosynthesis and metabolic regulation.